[COMMON] Fix a few bashisms

pointed out by checkbashisms:
- variable name HOSTNAME
- source instead of .
- variable increments
- sleep with suffix

And migrate a few shebangs to /bin/sh

Issue-ID: OOM-2643
Signed-off-by: Guillaume Lambert <guillaume.lambert@orange.com>
Change-Id: I82981bcff17e88cf824935b841ce37a585ddde00
diff --git a/kubernetes/robot/demo-k8s.sh b/kubernetes/robot/demo-k8s.sh
index 099f80c..5e4e216 100755
--- a/kubernetes/robot/demo-k8s.sh
+++ b/kubernetes/robot/demo-k8s.sh
@@ -222,7 +222,7 @@
 
 if [ $execscript ]; then
    for script in $(ls -1 "$DIR/$SCRIPTDIR"); do
-      [ -f "$DIR/$SCRIPTDIR/$script" ] && [ -x "$DIR/$SCRIPTDIR/$script" ] && source "$DIR/$SCRIPTDIR/$script"
+      [ -f "$DIR/$SCRIPTDIR/$script" ] && [ -x "$DIR/$SCRIPTDIR/$script" ] && . "$DIR/$SCRIPTDIR/$script"
    done
 fi